The field of streptococcal genetics has important links to both infectious diseases (streptococci cause more human illness than any other bacterial genus) and to modern genetics and molecular biology (the initial experiments indicating that DNA was the genetic material were carried out with Streptococcus pneumoniae). The current era of streptococcal genetics research began in the 1970's with much of the initial focus on plasmids associated with antibiotic resistance. As these studies have progressed, they have revealed the presence of unique biological phenomena such as bacterial sex pheromones and conjugative transposons. They have also made important contributions to the development of cloning systems, gene transfer systems, insertional mutagenesis systems, and immunological methods that are applicable to a wide variety of Gram-positive bacteria of medical and industrial importance. In addition, modern genetic and molecular techniques are being successfully developed and applied by researchers working on the organisms responsible for streptococcal diseases of major importance, such as pneumonia, rheumatic fever, glomerulonephritis, neonatal sepsis, and dental caries. Dramatic progress has also been made in using genetic approaches to analyze and to manipulate the microbial traits involved in the production of fermented dairy products by the "dairy streptococci" (lactococci). It has been observed repeatedly that the techniques developed and experimental findings obtained by researchers studying one streptococcal organism are often relevant to other streptococci, as well as many other Gram-positive genera. Thus, in previous conferences on Streptococcal Genetics held in 1981 and 1986, the participants found a unique opportunity to meet virtually all of the workers in the field, which has not been duplicated at any other conference. We request support for a third meeting, to be held in 1990, which has been prompted by the dramatic progress in Streptococcal Genetics that has occurred in the past three years. The meeting will consist of oral presentations by invited speakers, and poster presentations. Funds are requested for the travel expenses of 10 invited speakers and for 10 young investigators (postdoctoral associates and graduate students). In addition, a small amount is requested to help defray some of the other expenses of the meeting.